Chromatographic analyzer



March 6, 1962 M. c. BURK 3,023,605

CHROMATOGRAPHIC ANALYZER Filed Aug. 19, 1957 CHROMATOGRAPHIC COL U M N L l l" 5 1 FIG. 4

INVENTOR. M. C. BU RK BY m Unite States Patent 3,@23,605 Patented Mar. 6, 1962 3,023,605 CHROMATOGRAPHIC ANALYZER Marvin C. Burk, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Aug. 19, 1957, Ser. No. 678,951 2 Claims. (Cl. 73-23) efiluent from the column is analyzed by determining its thermal conductivity.

Since the thermal conductivity of the various components may vary, it is highly desirable or even essential to vary the sensitivity of the recording device in accordance with the thermal conductivity of the particular component under consideration and, more importantly. its concentration. Also, in order to obtain volume reproducibility between successive samples. a portion of the sample is trapped within a small chamber or sample loop, and this known volume of sample in the loop is thereafter displaced into the column by a carrier gas. This sequence of operations can advantageously be controlled by an oscillating valve movable to two positions by a reversible motor.

In accordance with this invention, an improved disc timer is provided to control the operation of the sample valve and simultaneously to insert variable'impedances in the recorder circuit so as to adjust the recorder sensitivity for the particular component being analyu d during a given period. The latter sequence of operations is controlled by detachable tabs at the edge of the disc which are placed to correspond to the time each particular component is present in the efiluent from the chromatographic column. The valve motor is controlled by another portion of the disc, for example, by openings formed therein to pass a beam of light at desired times as the disc rotates. The resulting control impulses are fed to a transistor type amplifier which actuates suitable relay devices to carry on the aforementioned control functions.

Accordingly, it is an object of the invention to provide an improved programming system for a chromatographic analyzer.

It is a further object to provide a timing and programming circuit which is simple. reliable in operation, and utilizes a minimum number of circuit components.

It is a still further object to insure provision of constant sample volumes to a chromatographic column during successive analyses of samples of similar composition.

Various other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic circuit diagram of the programming circuit;

FIGURE 2 is a top view of the timing disc;

FIGURE 3 is a detail view illustrating the manner in which tabs fit upon the timing disc; and

FIGURE 4 is a drawing of a recording.

Referring now to FIGURE 1, the flow of sample and carrier gas to a chromatographic column is controlled by a rotary valve 11 which, in the example shown, is provided with six ports. This valve can be oscillated between two angular positions by a motor 12 connected to the valve by a friction clutch 13.

In the first valve position, a sample from a line 14 passes through ports 1, 2 of the valve to a sample loop 15 which, in turn, is connected by valve ports 5, 6 to a pressure regulator 16, an exhaust pump 17, and a suitable vent, not shown.

A carrier gas, such as helium, passes from a line 18 to a first thermal conductivity cell 19 and, thence, through a line 20 and ports 3, 4 of the valve to the inlet of the column 10. The outlet of the column 10 is connected through a thermal conductivity cell 21 to a vent line 22. With the valve in this first position, therefore, the sample passes through the loop 15 to vent, and carrier gas passes through the column.

With the valve in its second position, the sample passes through ports 1, 6 to the pressure regulator 16 and vent while carrier gas passes through ports 4, 5 to the sample loop and, thence, through ports 2, 3 to the column 10, thus displacing the constant volume of sample trapped within the loop when the valve was in its first position.

The components appear in the column efiluent, in order of increasing sorbability, and thus unbalance a bridge circuit 23 incorporating the thermal conductivity cells 19 and 21, the temperature of the incoming carrier gas being compensated for by the inclusion of the cell 19 in the bridge circuit. The bridge circuit further includes fixed resistances 24, 25 connected in series with a potentiometer 26. A direct potential is applied-between the contactor of potentiometer 26 and ground at the junction between the cells 19, 21 by a regulated direct current power supply.

With a calibrating switch 30a, 30b in its upper posi-' tion, as shown, the output of the bridge appears between leads 31 and 32, the lead 32 being connected to a recorder input terminal 33a and to one fixed contact of each of a set 3411 to 340 of potentiometers, one such potentiometer being provided for each component to be analyzed. The other fixed terminal of each potentiometer 34 is connected to a terminal of a bank 351: of a selector switch 35 while the contactors of these potentiomcters are connected to the respective contacts of a selector switch bank 35b. The arm of contact bank 35b is connected through a normally closed contact set 36a of a relay 36 to another recorder input terminal 33b while the arm of the bank 350 is connected to the bridge output lead 31. The second bank contacts are connected together by a lead 37 while the first and third contacts of bank 35b are connected by a lead 38 to the lead 32.

With the switch 30 in its lower position, a calibrating voltage appears between the leads 31, 32 by virtue of a fixed resistance 40a and a potentiometer 40b.

When the selector switch is in one of its lower three positions, one of the potentiometers 34 is connected in circuit between the bridge output leads and the recorder input terminals, thus varying the sensitivity of the recorder input circuit in accordance with the particular component of the sample which is being analyzed. When the switch is on its second bank contact, the bridge is connected directly to the recorder input for zeroing or balancing purposes. When the selector switch is in its first or third position. the recorder input terminals 33 are short-circuited with the relay 36 die-energized and, whenever the relay 36 is energized, the recorder input-terminals are short-circuited by a lead 41. Finally, a calibrating voltage can be produced from the bridge, at will, by movement of the switch 30 to its lower position. t

The recorder has a chart drive motor 42, one terminal of which is neutral and the other terminal of which is connected to the arm of a contact bank 35g and to a normally open contact set 430 of a relay 43. An alternating current source 44 is connected to the second contact of the bank 35g. Thus, the recorder motor is energized when the relay 43 is actuated or when the selector switch is at its second contact posiuion.

The reversible valve motor 12 has two coils 12a and 12b, one terminal of each coil being connected to a voltage source 45 through a normally open contact set 46a of a relay 46. A lead 47 connects the other terminal of the coil 12a to the first contact of a bank 350' of the selector switch 35 and, similarly, the third contact of this bank is connected by a lead 48 to the other terminal of the coil 12b. A condenser 49 is connected across the leads 47, 48. The arm of the contact hank 35d is connected to a voltage source 50, and each of the other bank contacts is connected through one of a series 51a to 51d of indicator lamps to neutral.

Accordingly, with the selector switch in its first position, the motor 12 is rotated in one direction to move the valve to its first position where sample passes through the loop and carrier gas passes through the column 10, the clutch 13 permitting the motor to turn after the valve has reached its end position. When the arm of the bank d dwells on the third contact, the motor 12 is rotated in the opposite direction to move the valve 11 to its second position, both of these movements being controlled by the relay 46.

In accordance with the invention, the operation of the foregoing units is controlled by a novel disc timing device. This device incorporates a disc 52, FIGURES 1 and 2, fixed to the shaft of a motor 53 which is energized from an alternating current source 54 under the control of a switch 55. Detachably secured to the edge of the disc are a plurality of tabs 55a to 55g which are arranged to interrupt a beam of light passing from a lamp 56 to a photoelectric cell 57. Each tab has indentations 58 formed therein, FIGURE 3, which fit within circumferential slots 59 adjacent the edge of the disc 52. Thus, the tabs can be mounted on the disc or removed as desired, and can be placed at any deisred angular position along the edge of the disc.

A pair of openings 60a, 60b are formed in the disc, and these permit passage of a beam of light from a lamp 61 to a photoelectric cell 62. The lamps 56, 61 are connected in series with the secondary winding of a transformer 63, the primary winding of which is energized from the terminal 54.

The cell 57 is connected through a transistor amplifier composed of transistors 64, 65, and fixed resistances 66, 67, 68 and 69 to the operating winding of the relay 43, which is connected in series with the operating winding of the relay 36. In similar fashion, the photoelectric cell 62 is connected by a transistor amplifier including transistors 70, 71 and fixed resistances 72, 73, 74, and 75 to the operating winding of the relay 46 which is also connected in series with the operating winding of the relay 36.

Accordingly, when a tab 55 passes between the lamp 56 and cell 57, the relays 36, 43 are energized until the tab passes out of the path of the light beam. When an opening 60 passes between the lamp 61 and cell 62, the relays 36, 46 are energized until the opening passes out of the path of the beam, it being noted that the two transistor amplifiers are oppositely poled to accomplish this function.

The selector switch has a motor magnet 356 with a unit comprising a fixed resistor 76 and a series-connected condenser 77 in parallel therewith. One terminal of the motor magnet is connected to neutral while the other terminal is connected by a lead 78a to a normally open contact set 43b of the relay 43. The armature of this contact set is connected to a grounded condense 78 and the other fixed contact is connected to a direct current supply terminal 79. The motor magnet is further connected through an interrupter contact 80 to the terminals of a reset bank 35, of the selector swtich, the arm of this bank being connected to a direct current supply terminal 81 through a set 46b of normally open contacts of the relay 46.

It will be apparent, therefore, that each time a tab 55 passes between the lamp 56 and cell 57, the switch 35 makes one step due to the energization of relay 43 and the consequent closure of its contacts 43b. The selector switch is reset each time an opening 60 passes between the source 61 and cell 62 provided that the arm of the contact bank 35, dwells upon one of the three lower bank contacts, this action occurring through the operation of relay 46 and closure of its contacts 46b.

The overall operation of the system will now be described, assuming that the parts are in a position where the opening 600 is passing between the lamp 61 and cell 62, thus energizing relays 36 and 46. Therefore, the recorder input terminals are short-circuited, and the chart motor is stopped because no tabis between the cell 57 and the source 56. This is the point on the recording, FIGURE 4. This causes the selector switch to reset with the result that the bank arms move to their first position. Relay 36 short-circuits the recorder input terminals while relay 46 causes the motor 12 to move the valve 11 to its first position where the incoming sample flows through the loop 15 to vent and the carrier gas passes through the thermal conductivity cell 19 to the column 10.

When the opening 60a passes out of the path of the beam, the relay 46 is de-energized, thus interrupting the flow of current through the winding 12a of the motor 12. The relay 36 is de-energized but the recorder input terminals 33 remain short-circuited through the first contact of bank 35b.

When the leading edge of the tab 55b intercepts the beam between the lamp 56 and cell 57, relays 36, 43 are energized with the result that the selector switch moves to its second position. The recorder input terminals are short-circuited by the relay 36, and the chart motor starts to run by virtue of the closure of contacts 43a. The indicator lamp 51a is illuminated through the second contact of bank 35!: and a circuit is prepared connecting the bridge output terminals 31, 32 to the recorder input terminals 33 through the lead 37 and the second contact of banks 35a, 35b. During this interval, a straight line 91 appears on the recording.

When the tab 55b passes out of the path of the light beam, the relays 36, 43 are de-energized. The chart motor, however, does not stop because it is energized from source 44 through the second contact of bank 350. The circuit previously prepared through the recorder input terminals, lead 37 and the bridge becomes effective due to the opening of the circuit between the input terminals 33 at the contacts 36a which are now open. As a result, the recorder traces a horizontal calibrating line 92 representative of the bridge output, without attenuation, caused by the passage of carrier gas through the column 10, it being noted that the carrier gas passes through the thermal conductivity cell 21 from the column outlet.

Thereupon, the tab 55c intercepts the beam between the lamp 55 and cell 57, thus maintaining rotation of the chart motor and short-circuiting the recorder input terminals. This traces a horizontal line 93 on the chart, FIG- URE 4. The resulting closure of the contacts 43b steps the selector switch to its third position. When the tab 550 passes out of the path of the beam, the relay 36 is de-energized but the recorder input terminals remain short-circuited through the third contact of the bank 35b.

Movement of the chart motor stops upon the de-energization of the relay 43 and opening of contacts 43a.

46. Responsive to the closure of contacts 46a, the winding 12!) is energized through the third contact of bank 35d. thus causing the motor to run in reverse direction and move the valve 11 to its second position where the sample passes to the pressure regulator 16 and vent pipe, while carrier gas passes through the cell 19, sample loop 15, column 10, and cell 21 to the vent line 22, thus displacing a constant volume of the sample to be analyzed from the loop and causing it to fiow through the column. The components of the sample thereafter appear, in success1on, in the column effiuent in order of increasing atfinity for the sorptive material within the column.

When the opening 60!) passes beyond the beam, relay 46 is de-energizcd to stop the valve motor 12 and relay 36 is de-energized. However, the recorder input terminals remain short-circuited through the third contact of the bank 35b.

When the tab 55d intercepts the beam between the source 56 and cell 57, relay 43 is energized to start the recorder motor 42 through closure of contacts 43a, and to advance the selector switch to its fourth position through closure of the contacts 43b. This traces a horizontal line 94 on the recorder chart, FIGURE 4. The potentiometer 34a is thus placed in circuit between the bridge output leads 31, 32 and the recorder input terminals 33, but these latter terminals are short-circuited at this time by the closure of relay 36 and contacts 360.

When the tab 55d passes out of the path of the beam, analysis of the first component of the sample begins, this period lasting until the tab 55c intercepts the light beam. The length of this analysis circle is determined by the relative positions of the tabs 55d, 55c and is selected, by

virtue of a prior analysis of a sample having a generally similar constitution, so that the tabs can be readily placed in proper position upon the disc.

The described passage of tab 55d out of the path of the beam de-energizes the relay 36. thus open-circuiting the recorder input terminals 33. Thus. the potentiometer 3411 is inserted in the circuit between the bridge and recorder input terminals, and this unit is adjusted to give the proper recorder sensitivity based on the thermal conductivity of the first component of the sample which now appears in the ctlluent from the column 10 and passes through the cell 21. The chart motor is de-energized during this period due to the opening of the contacts 430, and the indicator lamp 511) is illuminated by virtue of the closure of the fourth contact of bank 3511. In this manner, a vertical line 95 is traced upon the recorder chart, the height of which represents the concentration of the least sorbable component of the sample.

As rotation of the disc continues, the tabs 55c and 55 in turn, intercept the light beam as the different components of the sample pass, in succession, from the column 10. As each tab intercepts the beam, the chart motor operates and the recorder input terminals are shortcircuited, thus producing short horizontal lines 96, 97 upon the recorder chart. During the interval between tabs, the chart motor stops and the appropriate potentionteter 34 is inserted in the recorder circuit to provide the proper recorder sensitivity for the component then under analysis, vertical lines 98, 99 being traced upon the recorder chart during these intervals which are representative of the concentration of the other components of interest in the sample.

The chart, FIGURE 4, indicates an analysis of three components. By the use of additional tabs, for example, tabs 55a and 55g as shown in FIGURE 2, and additional contacts, not shown, on the selector switch, additional components can be analyzed, as desired.

After the last component is analyzed, relay 46 is energized by the passage of opening 600 between the lamp 61 and cell 62. This applies power through the contacts 461: and the last contact of the reset bank 35f of the selector switch causing it to return to its original position. Thereupon, motor 12 is actuated to return the valve 11 to its first position to initiate a new cycle of analysis.

It will be evident that l have achieved the objects of the invention in providing a programming circuit for a chromatographic analyzer which is very flexible in operation. permits an accurate volumetric amount of the sampie to be fed to the column during each analysis cycle, and inserts the proper impedance in the recorder input circuit to sensitize the recorder for each component to be analyzed. Finally, positive efficient actuation of the relays is obtained through the use of the transistor amplificr circuits, and the tabs upon the timing disc permit any desired sample to be analyzed with the proper programming cycle.

1 claim:

I. In an analyzer, in combination, a rotatable disc. a series of tabs detachably secured to the edge of said disc in predetermined relative positions selected by virtue of a prior knowledge of the sample constituents, a recorder having a chart motor and a set of input terminals, means cooperating with said disc to provide a control impulse during the times a tab is positioned within a preselected area along the circumference of said disc, means responsive to such control impulses to energize the chart motor and short-circuit said input terminals when a tab is positioned within said area so as to produce a null record in said recorder of finite interval determined by said control impulse, the motor being de-energized and the input terminals open-circuited so as to receive a signal proportional to unbalance between a later-mentioned pair of thermal conductivity cells when no tab is positioned within said area, thus producing a bar-graph record in said recorder proportional in amplitude to said unbalance, a plurality of openings in said disc, means responsive to the positioning of one of said openings at a predetermined angular position to provide a second control impulse, a two-position valve, a sample loop cooperating therewith, a chromatographic column, a sample source, a source of carrier gas, a pair of thermal conductivity cells, said valve in its first position flowing sample from said source through said sample loop to vent, and flowing carrier gas through one cell to said column and then through the second cell, said valve in its second position flowing carrier gas through said one cell and said loop to said column and then through the second cell, and means for applying said second control impulses to said valve to cause it to alternate between its first and second positions.

2. In an analyzer, in combination, a rotatable disc, a series of tabs detachably secured to the edge of said disc in predetermined relative positions selected by virtue of a prior knowledge of the sample constituents, a recorder having a chart motor and a set of input terminals, a first light source and a first photoelectric cell cooperating with said disc to provide a control impulse during the times a tab is positioned within a preselected area along the cir' cumference of said disc, a transistor amplifier fed by said cell, selector switch means responsive. to amplified impulses from said amplifier to energize the chart motor and short-circuit said input terminals when a tab is positioned within said area so as to produce a null record in said recorder of finite interval determined by said control impulse. the motor being de-energized and the input. terminals open-circuited so as to receive a signal proportional to unbalance between a later-mentioned pair of thermal conductivity cells when no tab is positioned within said area, thus producing a bar-graph record in said recorder proportional in amplitude to said unbalance, a plurality of openings in said disc, a second light source and a second photoelectric cell responsive to the positioning of one of said openings at a predetermined angular position to provide a second control impulse, a transistor amplifier fed by said second cell, a two-position valve, a sample loop cooperating therewith, a reversible motor controlling said valve, a chromatographic column, a sample source, a source of carrier gas, a pair of thermal conductivity cells, said valve in its first position flowing sample from said source through said sample loop to vent, and flowing carrier gas through one thermal conductivity cell to said column and then through the second thermal conductivity cell, said valve in its second position flowing carrier gas through said one thermal conductivity cell and said loop to said column and then through the second thermal conductivity cell, said selector switch means controlling amplified second control impulses to cause said 0nd positions.

References Cited in the lilc of this patent UNITED STATES PATENTS Burrill Apr. 5, 1898 Knopp Apr. 18, 1933 Fisher July 17, 1934 Carlson Dec. 30, 1941 8 2,826,908 Skarstrom Mar. 18, 1958 2,833,151 Harvey May 6, 1958 2,875,606 Robinson Mar. 3, 1959 5 Y FOREIGN PATENTS 571,003 Great Britain Aug. 1, 1945 OTHER REFERENCES Article: Gas Chromatography, published in Oil and 10 Gas Journal, Dec. 17, 1956, pp. l26140. 

